Methods and apparatus for expressing body fluid from an incision

ABSTRACT

A sample of a body fluid such as blood or interstitial fluid is obtained from a body by lancing a portion of a user&#39;s skin, preferably in an area other than a finger tip, to form an incision. After the needle has been removed from the incision, a force is applied to depress the skin in a manner forming a ring of depressed body tissue in surrounding relationship to the incision, causing the incision to bulge and the sides of the incision to open, whereby body fluid is forced out through the opening of the incision. A stimulator member is mounted to an end of a lancet-carrying housing for applying the force. The stimulator member can be movable relative to the housing, and can be either heated or vibrated to promote movement of the body fluid.

PRIOR APPLICATIONS

This application is a continuation of Ser. No. 09/238,140 filed Jan. 28,1999 now U.S. Pat. No. 6,071,250 which is a continuation of Ser. No.08/858,043 filed May 16, 1997 now U.S. Pat. No. 5,951,493 claims benefitof copending applications Ser. No. 60/017,133 filed May 17, 1996; Ser.No. 60/019,918 filed Jun. 14, 1996; Ser. No. 60/023,658 filed Aug. 1,1996; Ser. No. 60/025,340 filed Sep. 3, 1996; Ser. No. 08/714,548 filedSep. 16, 1996; Ser. No. 08/710,456 filed Sep. 17, 1996; and Ser. No.08/727,074 filed Oct. 8, 1996 the disclosures of which are incorporatedherein by reference.

The present invention is related to inventions disclosed in thefollowing, commonly assigned U.S. applications: Ser. No. 08/857,680,entitles “Body Fluid sampling Device and Methods of Use”; Ser. No.08/858,045, entitled “Methods and Apparatus for Sampling Body Fluid”;Ser. No. 08/857,335, entitled “Disposable Element for Use in a BodyFluid Sampling Device”; and Ser. No. 08/858,042, entitled “Methods andApparatus for Sampling and Analyzing Body Fluid”. Ser. No. 08/960,866entitled “Synchronized Analyte Testing System”; Ser. No. 08/874,468entitled “Device for Determination of an Analyte in a Body Fluid”. Thedisclosures of those applications are incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to lancing devices and methods forobtaining samples of blood and other fluids from the body for analysisor processing.

BACKGROUND OF THE INVENTION

Many medical procedures in use today require a relatively small sampleof blood, in the range of 5-50 μL. It is more cost effective and lesstraumatic to the patient to obtain such a sample by lancing or piercingthe skin at a selected location, such as the finger, to enable thecollection of 1 or 2 drops of blood, than by using a phlebotomist todraw a tube of venous blood. With the advent of home use tests such asself monitoring of blood glucose, there is a requirement for a simpleprocedure which can be performed in any setting by a person needing totest.

Lancets in conventional use generally have a rigid body and a sterileneedle which protrudes from one end. The lancet may be used to piercethe skin, thereby enabling the collection of a blood sample from theopening created. The blood is transferred to a test device or collectiondevice. Blood is most commonly taken from the fingertips, where thesupply is generally excellent. However, the nerve density in this regioncauses significant pain in many patients. Sampling of alternate site,such as earlobes and limbs, is sometimes practiced to access sites whichare less sensitive. These sites are also less likely to provideexcellent blood samples and make blood transfer directly to test devicesdifficult.

Repeated lancing in limited surface areas (such as fingertips) resultsin callous formation. This leads to increased difficulty in drawingblood and increased pain.

To reduce the anxiety of piercing the skin and the associated pain, manyspring loaded devices have been developed. The following two patents arerepresentative of the devices which were developed in the 1980's for usewith home diagnostic test products.

Cornell et al. U.S. Pat. No. 4,503,856 describes a spring loaded lancetinjector. The reusable device interfaces with a disposable lancet. Thelancet holder may be latched in a retracted position. When the usercontacts a release, a spring causes the lancet to pierce the skin athigh speed and then retract. The speed is important to reduce the painassociated with the puncture.

Levin et al. U.S. Pat. No. 4,517,978 describes a blood samplinginstrument. This device, which is also spring loaded, uses a standarddisposable lancet. The design enables easy and accurate positioningagainst a fingertip so the impact site can be readily determined. Afterthe lancet pierces the skin, a bounce back spring retracts the lancet toa safe position within the device.

In institutional settings, it is often desirable to collect the samplefrom the patient and then introduce the sample to a test device in acontrolled fashion. Some blood glucose monitoring systems, for example,require that the blood sample be applied to a test device which is incontact with a test instrument. In such situations, bringing the fingerof a patient directly to the test device poses some risk ofcontamination from blood of a previous patient. With such systems,particularly in hospital settings, it is common to lance a patient,collect a sample in a micropipette via capillary action and then deliverthe sample from the pipette to the test device.

Haynes U.S. Pat. No. 4,920,977 describes a blood collection assemblywith lancet and microcollection tube. This device incorporates a lancetand collection container in a single device. The lancing and collectionare two separate activities, but the device is a convenient singledisposable unit for situations when sample collection prior to use isdesirable. Similar devices are disclosed in Sarrine U.S. Pat. No.4,360,016, and O'Brien U.S. Pat. No. 4,924,879.

Jordan et al. U.S. Pat. No. 4,850,973 and No. 4,858,607, disclose acombination device which may be alternatively used as a syringe-typeinjection device and a lancing device with disposable solid needlelancet, depending on configuration.

Lange et al. U.S. Pat. No. 5,318,584 describes a blood lancet device forwithdrawing blood for diagnostic purposes. This invention uses arotary/sliding transmission system to reduce the pain of lancing. Thepuncture depth is easily and precisely adjustable by the user.

Suzuki et al. U.S. Pat. No. 5,368,047, Dombrowski U.S. Pat. No.4,654,513 and Ishibashi et al. U.S. Pat. No. 5,320,607 each describesuction-type blood samplers. These devices develop suction between thelancing site and the end of the device when the lancet holding mechanismwithdraws after piercing the skin. A flexible gasket around the end ofthe device.helps seal the end around the puncture site until adequatesample is drawn from the puncture site or the user pulls back on thedevice.

Garcia et al. U.S. Pat. No. 4,637,403 and Haber et al. U.S. Pat. No.5,217,480, disclose combination lancing and blood collection deviceswhich use a diaphragm to create a vacuum over the wound site.

Erickson et al. U.S. Pat. No. 5,582,184, describes a means of collectingand measuring body fluids. This system uses a coaxial hollow lancet andcapillary tube disposed within a spacer member. The spacer member limitsthe depth of lancet penetration, and compresses body tissue around thelancet while the lancet is in the skin, for improving the flow ofinterstitial fluid to the incision. However, the incision may tend toclose around the lancet, thereby limiting the amount of body fluid thatcan be obtained.

Single use devices have also been developed for single use tests, i.e.home cholesterol testing, and for institutional use to eliminatecross-patient contamination multi-patient use. Crossman et al. U.S. Pat.No. 4,869,249, and Swierczek U.S. Pat. No. 5,402,798, also disclosedisposable, single use lancing devices.

U.S. Pat. Nos. 5,421,816; 5,445,611 and 5,458,140 disclose, as areplacement for invasive sampling, the use of ultrasound to act as apump for expressing interstitial fluid directly through intact (i.e.,non-lanced) skin. The amount of fluid which can be obtained by way ofsuch non-invasive vibration is minimal, however.

The disclosures of the above patents are incorporated herein byreference.

Even with the many improvements which have been made, the painassociated with lancing remains a significant issue for many patients.The need for blood sampling and the fear of the associated pain is alsoa major obstacle for the millions of diagnosed diabetics, who do notadequately monitor their blood glucose due to the pain involved.Moreover, lancing to obtain a blood sample for other diagnosticapplications is becoming more commonplace, and a less painful, minimallyinvasive device is needed to enhance those applications and make thosetechnologies more acceptable.

An object of the present invention therefore, is to provide a device anda method for obtaining a sample of bodily fluid through the skin whichis virtually pain free and minimally invasive, particularly bepenetrating less sensitive areas of the skin.

Furthermore, known lancing devices include manually actuable buttons fortriggering the lance-driving mechanism once the user has placed thedevice against his/her skin. Because the user knows the precise instantwhen the lancet will be triggered and pain will be felt, there is atendency for the user to jerk or raise the device at the instant oftriggering, which can lead to inconsistent skin penetration, or possiblyno penetration. Therefore, a further object of the invention is toprovide a lancing device which eliminates such a tendency on the part ofthe user.

Therefore, it is another object of the invention to provide a lancetcarrier which eliminates the above-mentioned shortcomings.

Another object of this invention is to provide a method which can resultin a sample of either blood or interstitial fluid, depending on thesample site and the penetration depth utilized. While there are nocommercially available devices utilizing interstitial fluid (ISF) atthis time, there are active efforts to establish the correlation ofanalytes, such as glucose, in ISF compared to whole blood. If ISF couldbe readily obtained and correlation is established, ISF may bepreferable as a sample since there is no interference of red blood cellsor hematocrit adjustment required.

Another object of this invention is to provide a method which can draw asmall but adjustable sample, i.e. 3 μL for one test device and 8 μL foranother test device, as appropriate.

Another object of this invention is to provide a method by which thedrawn sample is collected and may be easily presented to a testingdevice, regardless of the location of the sample site on the body. Thisapproach helps with infection control in that multiple patients are notbrought in contact with a single test instrument; only the samplingdevice with a disposable patient-contact portion is brought to the testinstrument. Alternatively, the disposable portion of a test device maybe physically coupled with the sampler so the sample can be broughtdirectly into the test device during sampling. The test device may thenbe read in a test instrument if appropriate or the testing system can beintegrated into the sampler and the test device can provide directresults displayed for the patient.

It is a further object of the invention is to provide a device forminimally invasive sampling comprising a reusable sampler and disposablesample lancet and collection device.

SUMMARY OF THE INVENTION

The present invention involves a method of obtaining a sample of fluidfrom a body. The method comprises applying a skin-lancing medium againsta skin surface to form an incision therein, removing the skin-lancingmedium from the incision; and thereafter applying a force to depress theskin in a manner forming a ring of depressed body tissue in surroundingrelationship to the incision, causing the incision to bulge and thesides of the incision to open, whereby body fluid is forced out throughthe opening of the incision.

The invention also relates to a device for sampling body fluid whichcomprises a housing having an open end, and a skin lancing mechanism forapplying a skin-lancing medium against a skin surface to form anincision therein and then remove the skin-lancing medium from theincision. A stimulator member is mounted to the housing at the open endthereof for movement relative to the housing. The stimulator memberextends about a longitudinal axis of the housing and is adapted toengage the skin surface to bulge and open the incision in response to apressing of the end face against the skin surface.

The invention also relates to a device for expressing body fluid from alanced skin surface, which comprises a housing, and a stimulatormechanism mounted to the housing at an end thereof. The stimulatormechanism includes a generally circular array of stimulator elementseach mounted to the housing for movement toward and away from alongitudinal axis of the housing. An actuator is mounted to the housingfor displacing the stimulator elements towards the axis.

The invention also relates to a device for expressing body fluid from alanced skin surface, which comprises a housing and a stimulator membermounted on the housing at an end thereof. The stimulator membercomprises a coil spring which is compressible toward the housing inresponse to being pushed against a user's skin in surroundingrelationship to a lanced portion thereof.

Another aspect of the invention relates to a device for expressing bodyfluid from a lanced skin surface which comprises a housing and a hollowstimulator member mounted at an end of the housing and adapted to engagea user's skin surface in surrounding relationship to a lanced portionthereof. In order to promote the flow of body fluid, the stimulatormember can be heated, or vibrated. If vibrated, the stimulator memberapplies an ultrasonic frequency to the skin surface.

The invention also relates to a device for expressing body fluid from alanced skin surface which comprises a housing and a hollow stimulatormember mounted at an end of the housing for longitudinal movementrelative to the housing and adapted to contact a user's skin surface insurrounding relationship to a lanced portion thereof. A motor is mountedin the housing and a reciprocatory mechanism is connected to the motorto be driven thereby, and is operably connected to the stimulator memberfor reciprocating the stimulator member along a longitudinal axis of thestimulator member.

BRIEF DESCRIPTION OF THE DRAWING

The objects and advantages of the invention will become apparent fromthe following detailed description of preferred embodiments thereof inconnection with the accompanying drawing in which like numeralsdesignate like elements and in which:

FIG. 1 is a longitudinal sectional view through a blood sampling deviceaccording to a first embodiment of the invention, with the lancetcarrier in an unarmed condition;

FIG. 2 is a view similar to FIG. 1, with the lancet carrier in an armedcondition;

FIG. 3 is a view similar to FIG. 2 after the lancet carrier has beentriggered and a lancet is penetrating the skin;

FIG. 4 is a fragmentary view similar to FIG. 1 after an incision hasbeen formed;

FIG. 5 is a view similar to FIG. 4 showing a stimulator member of thedevice being depressed to cause the incision to bulge and open;

FIG. 6 is a view similar to FIG. 5 after a stimulating action has beenperformed to form a drop of blood at the open end of the incision;

FIG. 7 is a fragmentary longitudinal sectional view through a secondembodiment of the invention;

FIG. 8 is a fragmentary longitudinal sectional view taken through athird embodiment of the invention;

FIG. 9 is a side elevational view of a fourth embodiment of theinvention pressed against a skin surface;

FIG. 10 is an end view of the device depicted in FIG. 9;

FIG. 11 is a view similar to FIG. 9 after the device has been compressedagainst the skin surface to bulge and open an incision;

FIG. 12 is an end view of the device in the condition depicted in FIG.11;

FIG. 13 is a fragmentary longitudinal sectional view taken through afifth embodiment of the invention while in a first state of operation;

FIG. 14 is a view similar to FIG. 13 with the device in a secondcondition of operation;

FIG. 15 is a fragmentary longitudinal sectional view taken through asixth embodiment of the invention in a first condition of operationthereof;

FIG. 16 is a view similar to FIG. 15 with the device in anothercondition of operation;

FIG. 17 is a view similar to FIG. 16 of yet a further condition ofoperation of the device;

FIG. 18 is a side elevational view, partly in longitudinal section ofyet another embodiment of the invention; and

FIG. 19 is a longitudinal sectional view taken through still a furtherembodiment of the invention.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION

A lancing device 10 (see FIG. 1) according to one preferred embodimentof the invention comprises an outer housing 12 having upper and lowerportions 14, 16 connected together, and an inner housing 18 fixed to theouter housing.

Mounted for vertical reciprocation in the upper portion 14 of the outerhousing 12 is a cocking mechanism 20 comprising a pull handle 22 towhich is fixedly secured a hollow draw tube 24. Fixed to an inner wallof the draw tube 24 is a draw ring 26.

Situated within the draw tube 24 is a draw bar 30 having a pair offlexible hooks 32 at its upper end. The hooks are releasably latched toa sleeve 34 which is movably disposed within the draw ring 26. A coilcompression spring 36 acts between a flange 33 of the sleeve 34 and aninner flange 38 of the draw ring 26.

A trigger sleeve 35 is mounted within the lower portion 16 of the outerhousing 12. A lower end of the trigger sleeve rests upon a first outerflange 37A of the inner housing, and a second outer flange 37B of theinner housing rests upon an inner projection 39 of the trigger sleeve.

At its lower end the draw bar 30 frictionally holds a skin-lancingmedium in the form of a disposable lancet 40 in which a needle 42 isdisposed. The draw bar 30 includes a flexible latch finger 44 that has aprojection 45 adapted to be received in a hole 46 of the inner housing18 (see FIG. 2) when the device is armed. A trigger member 49 is mountedin a hole 47 of the trigger sleeve 35 and includes an arm 48 extendingpartially into the hole 46. The trigger 46 includes an inclined camfollower surface 50.

A coil compression spring 52 acts between a top wall 54 of the innerhousing 18 and a shoulder 56 of the draw bar.

Slidably disposed within a lower end of the lower portion of the outerhousing is a firing tube 60 which includes an upper cam surface 62.Fixed to a lower end of the firing tube 60 is an outer hollow stimulatormember in the form of a cylindrical ring 64, having an end surface 65 ofgenerally frusto-conical shape so as to be oriented at a downward andinward inclination to generally face a longitudinal axis A of thedevice.

Disposed coaxially within the firing tube 60 and outer stimulator ring64 is an inner hollow stimulator member also in the form of acylindrical ring 66 having a frusto-conical end surface 67 also orientedat a downward and inward inclination.

The end surfaces 65 and 67 are of circular configuration when viewedalong the axis A, other configurations, such as polygonal, oval, etc.,are possible.

A coil compression spring 68 acts between an upper end of the outerstimulator ring 64 and a downwardly facing shoulder 70 of the innerstimulator ring 66.

The inner stimulator ring 66 includes a lance stop flange 72 adapted tobe engaged by a lance ring 74 of the lancet 40 as will be explained.

The first flange 37A of the inner housing rests upon a support sleeve 80which, in turn, rests upon an upper end of the inner stimulator ring 66.

In practice, when a fluid sample, such as blood or interstitial fluid,is to be taken from a user's body, a lancing device according to thepresent invention can be used to minimize pain. To do so, a region ofthe user's body having less sensitivity than, for example, a fingertip,is selected. Such a low-sensitivity region could be the user's forearmfor example. Initially, the handle 22 is pulled up to raise the drawbar30 until the projection 45 of the latch finger 44 snaps into the hole 44of the inner housing 18, as shown in FIG. 2. Simultaneously, the spring52 is compressed.

If the outer stimulator ring 64 is pressed against the user's skin S,e.g., on the selected forearm region FA, the ring 64 and its cam surface62 are moved upwardly to displace the trigger radially inwardly,whereupon the projection 45 of the latch finger 44 is disengaged fromthe hole 46. Accordingly, the spring 52 expands to displace the drawbar30 downwardly so that the needle 42 punctures the skin sufficiently deepto cut capillaries in the superficial vascular plexus, as shown in FIG.3. Simultaneously, the spring 68 is compressed. The extent ofdisplacement of the drawbar 30 is limited by engagement between thelance ring 74 with the lance stop 72.

Once lancing has occurred, the compressed spring 68 expands to raise thedrawbar, as well as the needle 42 and inner stimulator ring 66 from theskin (see FIG. 4).

The user then alternately applies and releases a downward force on theouter housing 12. Each time that a downward force is applied, the endface 65 of the outer stimulator ring 64 exerts a downward force F whichdepresses a ring-shaped portion of the skin and body tissue which isdisposed in surrounding relationship to the wound or incision I, causingthe wounded area to bulge while pulling apart the sides of the wound(see FIG. 5). Hence, fluid such as blood or interstitial fluid istrapped and pressurized so that it travels upwardly through thepulled-open end of the wound since the surrounding ring of depressedskin and body tissue restricts the outward flow of fluid. That action isenhanced by the fact that the force F is inclined inwardly toward theaxis A to force the fluid toward the bulged area.

When the downward force is released, the sides of the wound close, andfresh fluid flows toward the area of the wound to replace fluid whichhad been forced upwardly through the wound. As the downward force isreapplied, the above-described action is repeated and additional fluidis forced through the wound. Eventually, this “pumping” action resultsin the formation of a suitably large drop D of fluid (FIG. 6).

It will thus be appreciated that the present invention enables an amplesupply of blood, interstitial fluid or other body fluid to be obtainedrelatively painlessly from areas of the body which typically possesslesser amounts of such fluid as compared with the highly sensitivefingertip region.

Note that each time that the downward force is applied to the outerhousing, the outer stimulator ring 64 moves upwardly relative to theinner stimulator ring 66 so that the end surface 67 of the inner ring 66also contacts the skin surface S at a location inwardly of the outerface 65, thereby promoting the displacement of fluid inwardly toward thewound. However, the present invention can be practiced by a singlestimulator ring arrangement 64A as shown in FIG. 8.

While the surfaces 65, 67 are continuous, i.e., non-interrupted, it maybe desirable to provide either or both of those surfaces withcircumferentially spaced recesses 80 as shown in FIG. 7. The surface(s)65A, 67A will still depress a ring of body tissue surrounding the wound,but the areas of the ring corresponding to the location of the recesseswill be depressed to a lesser extent than the other areas. Those lesserdepressed areas will provide less resistance to fluid flow and will thusenable some fluid to leak past the ring, which would be beneficial inthe event that the user neglects to release the downward pressure on thedevice.

The stimulator member need not be in the form of a ring. As depicted inFIGS. 9-12, the stimulator member can be in the form of a helical spring90 formed by a flat strip 92. Such a spring would function in somewhatsimilar fashion to the double-ring arrangement of FIGS. 1-7 in that astimulator surface gradually comes into contact with the skin in aradially inward direction to aid in propelling blood or interstitialfluid toward the center axis. In that regard, FIGS. 9 and 10 depict acondition when the spring 90 is uncompressed. In contrast, FIGS. 11 and12 depict a condition wherein the spring is fully compressed. Shadedregions in FIGS. 10 and 12 represent contact between the spring and theskin. It will be appreciated that during compression of the spring, thecontact region of the spring progresses gradually radially inwardly,causing blood or interstitial fluid to be pushed toward the axis A andthus toward the bulged area of the skin.

Depicted in FIGS. 13 and 14 is yet another alternative embodimentwherein the outer stimulator ring 64B is interconnected to the innerstimulator ring 66B by levers 100 which are pivoted to the firing tube60B. Thus, upward sliding movement of the outer ring 64B is transmittedas a downward force to the inner ring 66B to slide the latter downwardlyand intensify the pumping action.

A further embodiment is depicted in FIGS. 15-17 wherein the firing tube60C has a carrier tube 102 affixed at a lower end thereof. Pivotablymounted on the carrier tube 102 is a circular array of levers 104 eachhaving an upper and lower end, each lower end carrying a stimulatorelement in the form of a roller 106. Each lever 104 is rotatable aboutan axis extending orthogonally relative to the axis of the housing.

An inner ring 110 is slidable up and down, either by manual force, or bya motor-driven cam (e.g., of the type disclosed later in connection withFIG. 19). That ring 110 has a beveled cam face 112 formed on its lowerend. When the device is pressed against the skin, following a lancingprocedure, the ring 110 is moved downwardly so that the cam face 112engages rollers 108 mounted on upper ends of the levers. Hence, thelevers 104 are rotated such that the lower rollers 106 are displacedinwardly and upwardly at a location disposed below the open end of thebulged wound to open the wound and force blood or interstitial fluidtoward the wound to form a drop D. When the levers are not contacted bythe cam face 112, the rollers 106 gravitate to a rest position shown inFIG. 15. Repeated applications of the downward force cause the drop tobecome gradually enlarged as explained earlier.

Depicted in FIG. 18 is an alternative embodiment similar to thatdepicted in FIGS. 1-6, except that the lower end surface of the outerstimulator ring 64D is provided with a hollow stimulator element 114which is electrically connected to a battery 116 mounted in an upper endof the device. The element can be either an electrical resistanceelement (i.e., a heater) or a vibrator such as a piezoelectrictransducer, intended to stimulate fluid flow. A heater will expand thecapillaries and make the blood or interstitial fluid less viscous andthus more flowable, in order to increase the amount of the body fluidsample.

On the other hand, if the element 114 is a vibrator, such as apiezoelectric transducer, vibrations can be created which stimulate theflow of body fluid. This could be achieved by operating the transducerto produce frequencies below 28,000 cycles per second. Alternatively,ultrasonic frequencies, i.e., frequencies above 20,000 cycles persecond, will create interferometric wave patterns inside the skin thatcause contractions forcing fluid upwardly from the wound. Thefrusto-conical shape 114A of the end face of the element will optimizethe creation of such wave patterns. It may be further beneficial toemploy a heater, such as an infrared emitter, mounted in the housingwhich vasodilates the capillaries to increase blood flow. Anotheradvantage of the use of such frequencies is that only minimal downwardforce to the device may be necessary since the wave patterns may producean ample pumping action.

FIG. 19 depicts a device which is not automatically fired, but ratherrequires manual actuation of lever 130 against a bias of a spring 132 toforce a trigger 134 to push a projection 136 out of a hole 138 (when theprojection extends into that hole).

Mounted in a housing 140 of the device are a battery 142 and electricmotor 144 connected to the battery to be actuated thereby. The motor 144rotates a sleeve 146 about the axis A. The sleeve includes a cam surface148 which engages a follower roller 150 mounted on a tube 152.

As the sleeve 146 rotates, the cam surface pushes the tube 152downwardly against the bias of a coil compression spring 154, to push aninner stimulator ring 156 repeatedly against a skin surface, therebypumping blood to the top of an incision in the same manner describedearlier herein. The inner stimulator ring 156 reciprocates along theaxis A within an outer stimulator ring 155. This embodiment eliminatesthe need for the user to pulsate the device up and down; the pumpingoperation is achieved automatically in response to actuation of thelever 130.

The cam mechanism 146 can be used in an automatically firing device,such as that disclosed in connection with FIG. 1.

It will be appreciated that the present invention enables a sampling ofblood or interstitial fluid to be taken from areas of the body, such asa forearm, that are less insensitive to pain, such as a forearm, thatare less insensitive to pain, despite the fact that those areastypically have relatively less fluid as compared, for example, tofingertips (which are highly sensitive to pain).

Therefore, there will be less reluctance on the part of users to have asampling procedure performed. For example, diabetics who experience arelatively high fear of pain will be less likely to neglect monitoringtheir blood glucose levels.

Another suitable skin lancing device that can be used to practice thepresent invention is that disclosed in concurrently filed applicationSer. No. 08/857,680, the disclosure of which is incorporated herein byreference.

In lieu of using a lancet as a skin-lancing medium, other skin-lancingmedia can be used, such as a laser, or known pneumatic or hydraulicinjectors of the type which inject pressurized gas or liquid against theskin. Such auto injectors are sold by Becton-Dickinson, for example, toinject insulin. By eliminating the insulin and merely injecting the gas(e.g., air or nitrogen) or liquid (e.g., water) at pressures above 30psi. an incision could be formed in the skin for taking samples of bodyfluid. Advantageously, small particles could be mixed with the gas topromote the tissue-cutting action. The particles could comprise carbonparticles of from 1 micron to 0.010 inches in diameter.

Although the present invention has been described in connection withpreferred embodiments thereof, it will be appreciated by those skilledin the art that additions, deletions, modifications, and substitutionsnot specifically described may be made without departing from the spiritand scope of the invention as defined in the appended claims.

What is claimed:
 1. A device for expressing body fluid from a lancedskin surface comprising: a housing; a retractable skin lancing mechanismmounted in the housing; a hollow stimulator member comprising astimulating end adapted to surround an incision when the stimulating endis pressed against the skin surface; and a heater electrically connectedto the stimulating end.
 2. The device of claim 1, wherein thestimulating end comprises having a peripheral surface adapted tosurround the incision when the stimulating end is pressed against theskin surface, the peripheral surface having a shape chosen from: apolygon and an oval.